Stabilizing and supporting means for a rotating element



Nov. 12, 1968 E. G. SAVAGE 3,410,029

STABI LIZING AND SUPPORTING MEANS FOR A ROTATING ELEMENT Filed May 24,1965 I VEN OR 71 EDMUND AVA 65 mg. 2 v

ATTORNEY United States Patent 3,410,029 STABILIZING AND SUPPORTING MEANSFOR A ROTATING ELEMENT Edmund G. Savage, North Brookfield, Mass,assignor to Norton Company, Worcester, Mass., a corporation ofMassachusetts Filed May 24, 1965, Ser. No. 458,023 11 Claims. (Cl.51-169) ABSTRACT OF THE DISCLOSURE Apparatus including a rotatingelement selectively either fully constrained radially thereof forrotation below its critical speed about a predetermined fixed axis oryieldably constrained radially thereof for rotation above its criticalspeed about its center of gravity subject also to radial displacementfrom the fixed axis due to its weight, and an assembly incorporating abiasing mechanism operative when the rotating element is yieldablyconstrained radially thereof to limit radial displacement of therotating element due to its weight.

The present invention relates to a stabilizing and supporting means fora rotating element and particularly to a stabilizing and auxiliarysupporting means for a rotating element operable to limit the radialdisplacement of a rotating elementwhile it is yieldably supported forrotation above its critical speed, for example, during the operation ofa balancing means supported by the rotating element and operableautomatically to balance the rotating element.

An automatic balancing device for a rotating element of the typeillustrated in Patent No. 3,107,550 of Backer et al. and in eopendingapplication Ser. No. 158,958 of Backer et al., now Patent No. 3,218,884,automatically operable to precisely balance a rotating element such as agrinding wheel or other cutting tool, when the rotating element issupported for rotation above its critical speed, is generally reliableand entirely satisfactory for applications such as those illustrated anddescribed in Patent Nos. 1,967,163 of Thearle, 2,142,021 of Ernst et211., 2,507,558 of Dall et al, and 3,107,550 of Backer et 211., alldisclosing balancing devices operable on the principle described inThearle 1,967,163.

However, it has been found that there are certain sizes andconfigurations of grinding wheel spindle assemblies, particularlyrelatively small sizes, in which the grinding wheel demonstrates anobjectionable degree of instability when it is supported for rotationabove its critical speed to provide for the automatic operation of thebalancing device. Furthermore, it has been found that excessive initialunbalance in a grinding wheel, such as that caused by the weight of anaccumulation of a grinding fluid in one sector of the grinding wheel,may cause momentary instability immediately after the grinding wheelspindle assembly has been released for rotation above its criticalspeed. In both such instances, it is [desirable to provide a stabilizingmeans effective to preclude unstable movement of the grinding wheelwhile it is supported for rotation above its critical speed and operablefor this purpose without significantly interfering with the operation ofthe balancing device.

In addition, it has been found that the deflection of a relatively largegrinding wheel is very substantial when the grinding wheel spin d-le isreleased for rotation above its critical speed, due to the combinedweight of the grinding wheel itself and the associated grinding wheelmounting means. In this instance, it is desirable to provide anauxiliary supporting means effective to limit the radial displacement ofthe grinding wheel while it is supported 3,410,029 Patented Nov. 12,1968 for rotation above its critical speed and operable for this purposewithout significantly interfering with the operation of the balancingdevice.

The instant invention contemplates a stabilizing and auxiliarysupporting means for a rotating element arranged so that it isinoperative and maintained out of engagement with a rotating elementwhile the rotating element is supported for rotation below its criticalspeed about a predetermined fixed axis and automatically operable whenthe rotating element is yieldably supported for rotation above itscritical speed to prevent unstable movement of the rotating element andto provide auxiliary support for the rotating element withoutinterfering with the automatic operation of a balancing device mountedupon the rotating element.

An object of the present invention is the provision of a stabilizingmeans for a rotating element operable to prevent unstable perturbationsof a rotating element yieldably supported for limited radialrdisplacement while it is rotating above its critical speed.

Another object is the provision of a stabilizing means for a rotatingelement operable to prevent objectionable instability while the rotatingelement is supported for rotation above its critical speed withoutinterfering with the automatic operation of balancing means for therotating element actuated while the rotating element is rotating aboveits critical speed.

Still another object is the provision of an auxiliary supporting meansfor a rotating element selectively rigidly supported for rotation abouta predetermined fixed axis and alternatively yieldably supported forrotation above its critical speed, said auxiliary supporting means beingeffective to limit the radial displacement of the rotating element fromits fixed axis of rotation while it is rotated above its critical speed.

Yet another object is the provision of an auxiliary supporting means fora rotating element yieldably supported for rotation above its criticalspeed operable to limit radial displacement of the rotating element dueto its weight without interfering with the automatic operation ofbalancing means for the rotating element.

A further object is the provision of an auxiliary supporting means for arotating element selectively supported by coacting releasable concentricload bearing means for rotation about a fixed predetermined axis andalternatively yieldably supported for rotation above its critical speedwhen the coacting load bearing means are released, said auxiliarysupporting means being effective tofacilitate re-engagement of theconcentric coacting bearing means.

A final object is the provision of a stabilizing and auxiliarysupporting means for a rotating element otherwise supported upon -ayieldable support with a relatively high spring rate for rotation aboveits critical speed, said stabilizing and auxiliary supporting meansincluding a biasing spring with a relatively very low spring rate.

Other objects and advantages of the instant invention will be evidentfrom consideration of the following description and the showing in theaccompanying drawings wherein:

FIG. 1 is a vertical section through a portion of a grinding machineillustrating the preferred embodiment of the stabilizing and auxiliarysupporting means of the instant invent-ion shown in operative relationto a rotating element comprising a grinding wheel mounted upon agrinding wheel spindle, and

FIG. 2 is a vertical section taken on line 22 of FIG. 1.

Referring now to the drawings wherein like reference numerals identifylike or corresponding parts, FIG. 1 illustrates a portion of a grindingmachine generally desiginated by the reference numeral 10 including awheel guard assembly 11 which may be fixedly secured by attachment meansnot illustrated to a wheel slide assembly 12 supporting a wheel spindleassembly including a relatively fixed portion 13 thereof mounted forrotation about a fixed horizontal axis by means of suitable supportingmeans therefore such as the spaced load bearing assemblies described andillustrated in Patent No. 3,218,884 and provided with external conicalload bearing surfaces 14 and internal cylindrical bearing surface 15. Asillustrated in FIG. 1, the relatively movable portion 16 of the wheelspindle comprises a wheel mounting hub supporting a grinding wheel 20and fixedly secured to a tapered elongated spring rod 21 in turnslidably supported concentrically within the relatively fixed portion 13of the wheel spindle. The relatively movable portion 16 of the wheelspindle also encloses and supports a balancing device 22 and a controlrod 23 therefore arranged and operable as illustrated and described indetail in Patent No. 3,218,884.

Since the spindle assembly and the co-operating balancing deviceillustrated in FIG. 1 are described in detail in Patent No. 3,218,884,neither the details of these features nor their modes of operation willbe described in detail herein, However, it should be noted that FIG. 1shows the relatively movable portion 16 positioned with the respectiveconical and cylindrical load bearing surfaces disengaged, so that thegrinding wheel 20 is yieldably supported on tapered spring rod 21 forrotation above its critical speed, and shows the balancing device 22released for an automatic balancing operation.

FIG. 1 also illustrates a cylindrical stub shaft 31 fixedly securedconcentrically of the relatively movable portion 16 of the spindleassembly so that it extends through an opening 32 in the wheel guard 11,and the preferred embodiment of the stabilizing and auxiliary supportingmeans of the instant invention generally designated by the referencenumeral 40.

Referring now to FIG. 2, the stabilizing and auxiliary supporting meansconsists of a supporting member 41 fixedly secured to the wheel guard 11by suitable attachment means such as machine screws 42 and including asocket portion 43 closed at one end by a threaded plug 44. Thesupporting member 41 includes a bracket portion 45 supporting a pivotpin 46 pivotally supporting an elongated lever 47 to which a suitableshoe 48 is fixedly secured for hearing engagement with the stub shaft31. The supporting member 41 also includes a lug portion 51 supporting athreaded adjustable stop member 52 secured by a lock nut 53. The lever47 is biased toward the stop member 52 by a biasing means comprising acompression spring 55 constrained within the socket portion 43 by thethreaded plug 44.

When the relatively movable portion 16 of the spindle assembly isdisplaced axially of the relatively fixed portion 13 of the spindleassembly into the position illustrated in FIG. 1 with the internalconical load bearing surfaces 17 out of bearing engagement with theexternal conical load bearing surfaces 14 and with the externalcylindrical load bearing surface 18 out of engagement with the internalcylindrical load bearing surface 15 so that the rotating assemblyincluding the grinding wheel 20 is yieldably supported upon and rotatedabove its critical speed by the tapered spring rod 21, the weight ofthis rotating assembly causes this assembly to be displaced radiallyfrom the fixed predetermined horizontal axis about which it rotatesbelow its critical speed when the conical load bearing surfaces 17 aredisposed in mutual engagement with the conical load bearing surfaces 14.This radial displacement of one end of the substantially elongatedspring rod 271, if relatively large, interferes with the re-engagementof the cylindrical load bearing surfaces and produces angulardisplacement of the grinding wheel 20 about a horizontal axis which mayresult in unstable perturbations that subject the apparatus to excessiveloads.

The possibility of objectionable instability can be avoided by providingthe stabilizing and auxiliary supporting means 40 arranged as shown inFIGS, 1 and 2 to coact with the stub shaft 31 and having a compressionspring 55 preloaded so that the lever 47 is biased against the stopmember 52 by a force approaching but slightly less than the forceexerted by the relatively movable portion 16 of the wheel spindle andthe grinding wheel 20 due to the weight of this rotating assembly.

When the tapered spring rod 21 is displaced to the left as seen in FIG.1 by a suitable actuating means, its initial displacement disengages therespective conical load hearing surfaces 14 and 17 and moves stub shaft31 into a position overhanging the surface of shoe 48 before therespective cylindrical load bearing surfaces 15 and 18 are completelydisengaged. Thereafter, continued displacement of the tapered spring rod21 into the position illustrated in FIG. 1 completely disengages therespective cylindrical load bearing surfaces 15 and =18 and finallyresults in operation of the control rod 23 to release the balancingdevice 22.

When the rotating assembly including stub shaft 31 assumes the positionillustrated in FIG. 1 and in FIG. 2 with the stub shaft 31 rotating inbearing engagement with shoe 48, the angular displacement of lever 47counterclockwise as seen in FIG. 2 is opposed by the compression spring55 so that radial deflection of the rotating assembly is relatively morelimited than would otherwise be the case with the result that angulardisplacement of the grinding wheel 20 about a horizontal axis issubstantially reduced.

Since successful opertaion of the balancing device 22 depends upon therotation of the rotating assembly about its center of gravity, thisrotation should desirably be at a speed substantially above the criticalspeed of the rotating assembly, this critical speed being dependent uponthe spring rate of the entire structure upon which the rotating assemblyis yieldably supported. Accordingly, when a stabilizing and auxiliarysupporting means 40 including a compression spring 55 is used asdescribed above in association with the tapered spring rod 21, thecontribution of the compression spring 55 to the overall resilience ofthe supporting arrangement must be taken into account in designing thesupporting arrangement to assure the proper operation of the balancingdevice 22. A desirable practical arrangement which does not require anydesign change in the tapered spring rod 21 makes use of a compressionspring 55 selected so that it has a spring rate very much lower than thespring rate of the tapered spring rod 21. In this case, the spring rateof the yieldable supporting structure is dependent almost entirely uponthe spring rate of the tapered spring rod 21 so that the addition of astabilizing and auxiliary supporting means 40 including such acompression spring 55 has a negligible effect on the yieldablesupporting structure including both the tapered spring rod 21 and thestabilizing and auxiliary supporting means 40.

When the weight of the rotating assembly is increased substantially asby the use of a thicker grinding wheel 20, the preload on compressionspring 55 can be increased accordingly by substituting a longercompression spring with the same spring rate or by providing a suitableshim between the compression spring 55 and the threaded plug 44 tofurther compress the compression spring 55. If necessary, the preload oncompression spring 55 may also be varied in a similar fashion from arelatively low preload for the relatively light worn stub of a grindingwheel 20 to a relatively high preload for a relatively heavy newgrinding wheel 20. However, as a practical matter, the stabilizing andauxiliary supporting means 40 will commonly produce an adequatestabilizing effect throughout the life of a given grinding wheel 20 ifit is preloaded so that it exerts a force alrnost but not quite equal tothe force exerted due to the minimum weight it must oppose, that is theweight of the relatively movable portion 16 of the wheel spindle and theweight of a fully worn stub of a grinding wheel 20.

While the preferred embodiment of the instant invention is illustratedand described as including a conventional coil compression spring 55 asthe biasing means, a constant force spring may be substituted.Alternatively, the biasing means may be so arranged that it is dependentupon resistance supplied by pneumatic or hydraulic pressure to limit theradial displacement of the rotating assembly. Clearly any one of theseconfigurations will be sufli ciently resilient to accommodate thelimited radial excursions of the rotating assembly indicated by theshowing in phantom lines in FIGS. 1 and 2 which necessarily occur as anunbalanced rotating assembly is rotated above its critical speed so thatit rotates about its center of gravity rather than about its geometriccenter.

Since the stabilizing and auxiliary supporting means of the instantinvention is particularly useful primarily to prevent objectionableinstability in relatively small grinding machines where available spacefor mounting the stabilizing means is limited, the generally L-shapedconfiguration of the stabilizing and auxiliary supporting means 40 bestillustrated in FIG. 2 is the preferred embodiment of the instantinvention. Alternatively, where space permits, and particularly onrelatively large grinding machine assemblies, where the stabilizing andauxiliary supporting means 40 may be useful primarily as an auxiliarysupport, it may include an elongated supporting member mounted upon afixed support such as the wheel guard 11 and disposed radially of thegrinding wheel and vertically beneath the axis of the wheel spindle sothat the compression spring is confined within a hollow plunger slidablymounted within a suitable socket portion of the supporting member to actagainst the closed end of the hollow plunger, fitted with a suitableshoe 48 and arranged to be engaged by a stop member either integral withor supported by the supporting member. However, either of theseconfigurations will perform both the stabilizing and the supportingfunctions. Therefore, it should be understood that this alternativeembodiment of the stabilizing and auxiliary supporting means 40 willfunction in the same manner as the embodiment described in detail abovein connection With the showing in FIG. 2.

The description provided above is to be considered ill-ustrative ratherthan in a limiting sense, since various modifications of this device arecontemplated within the scope of the appended claims.

I claim:

1. Apparatus comprising,

a rotating element so disposed as to be subject to a predetermined forceapplied radially thereto in a predetermined direction,

a first rotatable supporting means for said rotating element mounted torotate about a predetermined fixed axis,

releasable coupling means having opposed load bearing surfaces operativewhen they are disposed in mutual engagement to fully constrain saidrotating element radially relative to said first supporting means forrotation therewith about said fixed axis below the critical speed ofsaid rotating element,

a radially yieldable second rotatable supporting means t for saidrotating element connected to said rotating element and operative whensaid coupling means is released to rotate said rotating element aboveits critical speed about its center of gravity,

and stabilizing and auxiliary supporting means for said rotatingelement, constructed and arranged to be maintained inoperative when saidreleasable coupling means is operative and to be operative when saidsecond supporting means is operative, yieldably to oppose and therebylimit radial displacement of said rotating element due to saidpredetermined force, said stabilizing and auxiliary supporting meanscomprising,

support means fixedly mounted radially relative to said first supportingmeans,

shoe supporting means mounted upon said support means for movementradially relative to said first supporting means,

shoe means mounted upon said shoe supporting means for movementtherewith and disposed for engagement with said rotating element,

biasing means mounted upon said support means and operative to displacesaid shoe supporting means toward said rotating element,

and fixed stop means mounted on said support means disposed so as tolimit displacement of said shoe supporting means and thereby maintainsaid biasing means inoperative when said coupling means is operative.

2. Apparatus as described in claim 1, wherein said biasing meanscomprises,

a spring preloaded by the application thereto of a force less than butclose to said predetermined force.

3. Apparatus as described in claim 1, wherein said biasing meanscomprises,

a spring having a spring rate negligible relative to that of said secondsupporting means and preloaded by a force substantially equal to butless than said predetermined force.

4. A machine tool comprising,

a rotating tool assembly so disposed as to be subject to a predeterminedforce applied radially thereto in a downward direction due to the weightof said rotating tool assembly,

a first rotatable supporting means for said rotating tool assemblymounted to rotate about a predetermined fixed axis,

releasable coupling means having opposed load bearing surfaces operativewhen they are disposed in mutual engagement; to fully constrain saidrotating tool assembly radially relative to said first supporting meansto secure said rotating element for rotation With said first supportingmeans about said fixed axis below the critical speed of said rotatingtool assembly,

a radially yieldable second rotatable supporting means for said rotatingtool assembly connected to said rotating tool assembly and operativewhen said coupling means is released to rotate said rotating toolassembly above its critical speed about its center of gravity,

and stabilizing and auxiliary supporting means for said rotating toolassembly, constructed and arranged to be maintained inoperative whensaid releasable coupling means is operative and to be operative whensaid second supporting means is operative, yieldably to oppose andthereby limit downward radial displacement of said rotating toolassembly due to the weight of said rotating tool assembly.

5. A machine tool as described in claim 4, wherein said stabilizing andauxiliary supporting means comprises, support means fixedly mountedradially relative to said first supporting means,

shoe supporting means mounted upon said support means for movementradially upward relative to said first supporting means,

shoe means mounted upon said shoe supporting means for movementtherewith and disposed for engagement with said rotating tool assembly,

biasing means mounted upon said support means and operative to displacesaid shoe supporting means toward said rotating tool assembly,

and fixed stop means mounted on said support means disposed so as tolimit displacement of said shoe supporting means and thereby maintainsaid biasing means inoperative when said coupling means is operative.

6. A machine tool as described in claim 5, wherein said biasing meanscomprises,

said biasing means comprises,

a Spring having a spring rate negligible relative to that of said secondsupporting means and preloaded by a force substantially equal to butless than said predetermined force due to the weight of said rotatingtool assembly.

8, A grinding machine comprising,

a rotating grinding wheel assembly so disposed as to be subject to apredetermined force applied radially thereto in a downward direction dueto the weight of said rotating grinding wheel assembly,

a rigid first rotatable supporting means for said rotating grindingwheel assembly mounted to rotate about a predetermined fixed axis,

releasable coupling means having opposed load bearing surfaces operativewhen they are disposed in mutual engagement; to fully constrain saidrotating grinding wheel assembly radially relative to said firstsupporting means to support said grinding wheel assembly for rotationwith said first supporting means about said fixed axis below thecritical speed of said rotating grinding wheel,

a fiexible radially yieldable second rotatable supporting means for saidrotating grinding wheel assembly connected to said rotating grindingwheel assembly and operative when said coupling means is released torotate said rotating grinding wheel assembly above its critical speedabout its center of gravity,

balancing means mounted upon said grinding wheel assembly operative tobalance said grinding wheel assembly when said second supporting meansis operative to rotate said grinding wheel assembly about its center ofgravity,

and stabilizing and auxiliary supporting means for said grinding wheelassembly, constructed and arranged to be maintained inoperative whensaid releasable coupling means is operative and to be operative whensaid second supporting means is operative, yieldably to oppose andthereby limit downward radial displacement of said rotating grindingwheel assembly due to the weight of said rotating grinding wheelassembly, without precluding operation of said balancin g means.

9. A grinding machine as described in claim 8, wherein said stabilizingand auxiliary supporting means comprises,

support means fixedly mounted radially relative to said first supportingmeans,

shoe supporting means mounted upon said support means for movementradially relative to said first supporting means,

shoe means mounted upon said shoe supporting means for movementtherewith and disposed for engagement with said rotating grindingmachine assembly,

biasing means mounted upon said support means and operative to displacesaid shoe supporting means toward said rotating grinding wheel assembly,

and fixed stop means mounted on said support means disposed so as tolimit displacement of said shoe supporting means and thereby maintainsaid biasing means inoperative when said coupling means is operative.

10. A grinding machine as described in claim 9, wherein said biasingmeans comprises,

a spring preloaded by the application thereto of a force less than butclose to said predetermined force due to the weight of said rotatinggrinding machine assembly.

11. A grinding machine as described in claim 9, wherein said biasingmeans comprises,

a spring having a spring rate negligible relative to that of said secondsupporting means and preloaded by a force substantially equal to butless than said predetermined force due to the weight of said rotatinggrinding wheel assembly.

References Cited JAMES L. JONES, J R., Primary Examiner.

